High resolution absorption spectrum of CO2between 1750 and 2000 Å

The absorption spectrum of CO2 gas between 1750 and 2000 Å has been photographed at high resolution and proves to be extremely rich in bands with considerable rotational fine structure. In spite of the great complexity, we have been able to achieve a coherent preliminary analysis of 9 bands defining an excited state bending progression and which are among the stronger bands in this spectral region. The symmetry species obtained for the upper levels is consistent with their assignment to the 11A2 state, rendered vibronically allowed by excitation of one quantum of the asymmetric stretching v′3(b2) vibration. The assignments are discussed in relation to recent ab initio calculations. Many perturbations are present in the spectra and some of these have been satisfactorily explained.